How Do Veterinarians Diagnose Canine Atopic Dermatitis?

Valerie Fadok, DVM, PhD, DACVD, dermatologist in the Veterinary Specialty Team at Zoetis, discusses the different factors that veterinarians should consider before diagnosing patients with atopic dermatitis.

Interview Transcript (slightly modified for readability)

“I think the most common things we’re seeing with regard to advancement in diagnosis of atopic dermatitis in dogs go[es] back to our improved understanding of how its caused. Thirty some years ago, when I was starting up, we knew that atopic dermatitis occurred, but we were very focused on one aspect and that’s the allergic antibody, IgE. [IgE] is the basis of our diagnostic tests, whether we skin test dogs, or whether we serum test dogs. But what we’ve learned is that the disease is so much more than just the IgE.

The immune system is deranged so it is abnormal; dogs react to things that don’t matter. Pollens aren’t really dangerous to the body but those are some of the things that dogs react to. As a consequence of that, I think we’ve learned as far as diagnosis, that there are certain criteria that we use to make us suspicious. We don’t really have a diagnostic test, but we look at features in the dog’s background. Is it the right breed? Did the itch develop before three years of age? We know that that happens. The feet are almost always involved. Dogs have redness around the eyes, the muzzle, the feet, the belly, the armpits, and usually, unless they have co-existing flea allergy, the back of their body is normal.

This is a disease that affects the face and the central part of the body. We diagnose atopic dermatitis based on this history and clinical signs, but we always have to rule out other causes of itch. We recommend treating for ectoparasites, like fleas and scabies, and consider food allergy if these are dogs that are itchy year-round. Those are the things we’re looking at and then when we control ectoparasites and infections and we figure out whether the dog has food triggers or not, then we’re left with the diagnosis of atopic dermatitis, which is a lifelong disease, so we have to have a good way to manage it.”